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%I #16 Aug 12 2022 12:38:23
%S 1,3,21,59,198,703,2568,8421,26165,78074,229881,668082,1928220,
%T 5523946,15745682,44666804,126251748,355692380,999498933,2802212026,
%U 7841587533,21907928927,61123152811,170333279738,474197771123,1319004492132,3666181193067,10183729521212
%N a(n) is the number of free polyominoes of width 4 and size n.
%C The sequence can be generated using a series of recursive formulas in a fashion similar to A352720 and A353067. These require respectively around 500 and 62000 formula lines, whereas a(n) requires about 10 million lines.
%H John Mason, <a href="/A354850/b354850.txt">Table of n, a(n) for n = 4..100</a>
%H John Mason, <a href="/A354850/a354850.txt">Java programs for calculating sequence, valid also for widths 2 and 3</a>
%Y Cf. A000105, A352720, A353067.
%K nonn
%O 4,2
%A _John Mason_, Jun 08 2022